The presently described technology relates generally to stretchable elastic laminates. More specifically, the present technology relates to stretchable elastic laminates formed from an elastic melt layer and a non-woven layer and having zones of increased cross-direction (CD) elongation which enable the laminate to have improved recovery after stretch. The elastic laminate also may have low stretch zones that facilitate attachment of the elastic laminate to nonstretchy films, laminates or hooks in a disposable article.
Disposable absorbent articles (e.g., disposable diapers for children or adults) often include elastic features designed to provide enhanced and sustainable comfort and fit to the wearer by conformably fitting to the wearer over time. Examples of such elastic features may include, for example, elastic waistbands, elastic leg cuffs, elastic side tabs, or elastic side panels so that the absorbent article can expand and contract to conform to the wearer in varying directions. Additionally, such elastic features are often required to be breathable to provide a desired level of comfort to the wearer's skin.
Further, the elastic features of disposable absorbent articles may be made of stretchable elastic laminates. A stretchable elastic laminate typically includes an elastic film and a non-woven fabric. More particularly, the elastic film is typically bonded to the non-woven fabric to form the stretchable elastic laminate.
A nonwoven elastomeric laminate is disclosed, for example, in U.S. published application No. 2005/0287892 A1. According to the disclosure, the nonwoven web is one in which the fibers are thermally bonded to form the web material. An elastomeric film is directly bonded to the nonwoven web layer by feeding the elastomeric film and the nonwoven web to the nip between two calender rollers. Pressure between the calender rollers ranges from about 0.25 to about 5 bar. Pressures at the lower end of the range are stated as being preferred, in order to insure that the elastomeric material does not become deeply embedded in the nonwoven web.
Bonding the elastic film to the non-woven fabric typically requires a secondary bonding operation. For example, U.S. Pat. No. 6,069,097 (the '097 patent) describes forming a stretchable elastic laminate using a secondary bonding operation to bond an elastic film to a non-woven fabric. The '097 patent discloses using a heated embossing roller and a chilled roller to bond a co-extruded elastic film to a spunlace non-woven fabric to form the composite elastic sheet, (col. 14, lines 7-20). Further, the '097 patent discloses that the composite sheet should be bonded in a particular pattern, namely that the composite should be bonded in a direction perpendicular to the direction of elongation, and also that the bond sites should be positioned so that bond sites on either side of the elastic sheet do not overlap with the bond sites on the other side.
Additionally, for example, U.S. Pat. App. Pub. No. 2004/0121687 (the '687 publication) describes forming a stretchable elastic laminate using a secondary bonding operation to bond an elastic film to a non-woven fabric. The '687 publication discloses that a stretchable laminate is formed using nip rolls 46, 48 to bond an elastomeric sheet 14 to an extensible nonwoven web 12 (paragraph 0088). According to the '687 publication, the extensible nonwoven web 12 may be laminated to the elastomeric sheet by a variety of processes including but not limited to adhesive bonding, point bonding, ultrasonic welding and combinations thereof” (paragraph 0090).
Furthermore, the '687 publication also describes the extensible nonwoven web 12 as “a necked spunbonded web, a necked meltblown web or a necked bonded carded web” (paragraph 0065). Moreover, stretching the nonwoven web in one direction not only causes necking in the other direction, but may also cause the nonwoven web to become thicker. A variation in thickness may require more complicated set-up procedures and additional processing equipment when utilizing the nonwoven web in different manufacturing operations, thus resulting in increased manufacturing costs. Further, necking of the nonwoven web may cause orientation of the fibers which may result in a striated appearance that may not be aesthetically pleasing.
Employing a secondary bonding operation to form the stretchable laminate typically increases the production cost of the stretchable elastic laminate. Thus, there is a need for a low-cost stretchable elastic laminate that does not require a secondary bonding operation.
Improving the elasticity of the stretchable elastic laminate typically requires stretch activation, which typically requires a secondary stretching operation. For example, U.S. Pat. No. 6,313,372 (the '372 patent) relates to a stretch-activated plastic composite. According to the '372 patent, “it may be desirable that such stretch activation be done either prior to or during production of a product using the composite” (col. 4, lines 37-39).
Additionally, for example, the '687 publication describes stretching a non-woven fabric with two pairs of rollers, each pair of rollers operating at a different speed. More particularly, the '687 publication describes necking an extensible nonwoven web 12 using a first nip 30, including nip rolls 32, 34 turning at a first surface velocity, and a second nip 36, including nip rolls 38, 40 turning at a second surface velocity that is higher than the first surface velocity (paragraph 0085). The '687 publication also describes mechanically stretching the laminate 50 using grooved rolls 58, 60 (paragraph 91) or a tenter frame 66 (paragraph 92).
Therefore, the secondary stretching operation typically increases the production cost of the stretchable elastic laminate. Thus, there is a need for a low-cost stretchable elastic laminate with improved elasticity that does not require a secondary stretching operation.